So far, the Connecticut-based subsidiary of United Technologies Corp. has committed a couple of decades and roughly $10 billion to develop its geared turbofan (GTF) technology.

Unfortunately, it looks as if we'll have to wait a bit longer for this piece of newfangled equipment to hit its stride.

Even though PurePower engines entered service in 2016, the number of aircraft using the engine remains limited because of a number of teething problems.

Airbus

The first issues came to light that year when Qatar Airways' Airbus A320neos experienced uneven cooling in their GTF engines. Uneven cooling could lead to deformations and parts rubbing against one another while prolonging turnaround times between flights. As a result, the airline deemed the engines unable to meet its performance requirements.

In December, Qatar replaced its troubled order for 50 A32oneos with an order for 50 larger A321neos. This time around, the airline is expected to use engines from rival CFM International instead of Pratt & Whitney.

In February, IndiGo, an Indian low-cost airline, announced it had to replace 69 engines in 18 months on its fleet of around 30 A320neo jets, Bloomberg reported.

Around the same time, Airbus had to temporarily halt deliveries of GTF-powered jets because of on-going issues with the engine.

The problems culminated with India's aviation authority, DGCA, grounding 11 PurePower GTF-powered Airbus A320neo jets. According to the Economic Times, the decision was made after GTF powered Airbus jets suffered three midflight engine failures in two weeks. The failures have been attributed to an issue with a seal in the engine's high-pressure compressor.

Pratt & Whitney

In a statement to Business Insider, Pratt & Whitney said it was aware of the decision made by the DGCA and that it, along with Airbus, is fully committed to maintaining the airworthiness of its planes.

The statement went on to explain that Pratt & Whitney took immediate action last month after identifying an issue related to the knife-edge seal in the high-pressure compressor of 43 PW1100G-JM engines designed for the Airbus A320neo. Pratt received "all necessary approvals" from European aviation regulators for the changes it made to the engine by February 21, the company said. According to Pratt & Whitney, it began shipping updated engines by March 1.

It should be noted that modern twin-engine jetliners are designed to operate on a single engine.

Pratt & Whitney's new geared turbofan engine is still a game changer

The idea of a geared turbofan engine centers on the principle of a bypass ratio. Modern turbofan engines produce thrust in two manners.

First, there are the compressors and combustion chamber at its core. It's the part of the engine we most commonly associate with a jet. Then there's the fan at the front of the powerplant that's driven by the jet core. It directs air through bypass compartments around the core of the engine.

The bypass ratio is the proportion of the air that bypasses the core versus the amount that goes through it. Generally speaking, a higher bypass ratio means quieter, more efficient, and more powerful engines.

Pratt & Whitney

In conventional turbofan engines, a bypass ratio reach can reach as high as 9-to-1. Pratt's PurePower GTF engines have a bypass ratio of 12-to-1.

To increase bypass ratio, engine manufacturers have to increase the length of its fan blades. However, if elongated enough, the speeds achieved at the tip of the blades will be so fast that it generates unwanted vibrations.

This is where the "gear" in geared turbofan comes into the picture, aviation industry analyst Richard Aboulafia told Business Insider.

"You can get as high as eight or 10-to-1 without a gear, but to move beyond that ratio you need something to slow down the fans so they don't go too fast basically," Aboulafia said. "And the gearbox does that for you."

According to Pratt & Whitney, its engine's gearbox doesn't just slow the fan, like the transmission in a car; it also helps the fan spin at its optimal speed. And the results are incredible.

Airbus

Compared to current generation engines, Pratt claims it can achieve 16% better fuel efficiency and 50% lower emissions and is 75% quieter.

In fact, SWISS and Air Baltic have reported their GTF powered C Series jets have returned even better fuel economy than Bombardier's projections.

Fortunately for Pratt & Whitney, all the problems the company's next-generation engines have encountered do not point to fundamental flaws with the technology and can be fixed, Aboulafia said. It'll just take time.